The present invention relates to improvements in apparatus for processing exposed photographic films or exposed webs of photographic paper, and more particularly to improvements in continuous processors for webs or strips of exposed photographic material. Still more particularly, the invention relates to improvements in processors of the type disclosed in the aforementioned copending application Ser. No. 783,800 of Erwin Laar.
The application of Laar discloses a processor wherein the material to be developed is transported through several tanks which contain supplies of a liquid processing medium and wherein the temperature of the liquid is maintained within a desired narrow range by a composite heating device. The liquid is withdrawn from the lower portions and is returned to the upper portions of the tanks by flowing through a pump, thereupon through the heating device and finally through a filter. The apparatus of Laar is designed to insure that the temperature of the liquid which reenters the tanks is always maintained within an extremely narrow optimum range. As a rule, the conduits through which the liquid flows from the outlets to the inlets of the respective tanks are flexible hoses which are secured to the nipples of the inlets and outlets of the respective tanks by suitable clamps or the like. It can happen, from time to time, that a hose becomes detached from the respective nipple or nipples, and/or that a hose develops a leak. If the hose or hoses are disconnected or permit liquid to escape for another reason, the pump is likely to be damaged or destroyed if its motor continues to run while the intake of the pump does not receive any or receives negligible quantities of liquid. Furthermore, the heating device is likely to be damaged or destroyed (due to overheating) if it remains operative while no liquid flows therethrough. Additional damage can result under the action of escaping liquid which often contains corrosive chemicals. Such liquid is not only likely to contaminate the surrounding area but can also constitute a health hazard to the attendants. Furthermore, the cost of certain processing liquids is very high. Finally, the escape of processing liquid and/or the failure of processing liquid to circulate at an optimum rate and/or to receive requisite quantities of regenerator solution (replenisher) per unit of time invariably results in damage to or destruction of the processed material, such as webs of exposed photographic paper which are to be severed after development to yield discrete customer prints. The paper will be damaged if the supply of liquid in the tank or tanks of the processor drops below a predetermined level.